<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <link rel="stylesheet" href="bootstrap/css/bootstrap.css">
</head>
<body>
                <ul class="nav nav-tabs">
                        <li class="active"><a href="#">苹果</a></li>
                        <li class="dropdown">
                        <a href="#" class="dropdown-toggle" data-toggle="dropdown">小米
                        <span class="caret"></span></a>
                        <ul class="dropdown-menu" >
                        <li><a href="#">小米手机</a></li>
                        <li><a href="#">小米电脑</a></li>
                        <li><a href="#">小米平板</a></li>
                        </ul>
                        </li>
                        <li><a href="#">华为</a></li>
                        </ul>


    <script src="bootstrap/js/jquery-3.3.1.js"></script>
    <script src="bootstrap/js/bootstrap.js"></script>
</body>
</html>